An electrical test (that is, an electrical inspection) of an integrated circuit is generally performed with use of an apparatus for electrically connecting a conductive portion such as a wiring pattern formed on a surface of a wiring board to an electrode portion such as a lead electrode, a pad electrode, a bump electrode, a projection electrode of the integrated circuit.
As one of the electrical connecting apparatuses of this kind, there is one using a plurality of J-shaped or L-shaped contacts each having a probe rear portion extending in the right-left direction, a deformation portion continuing into the tip end side of the probe rear portion and having an external surface deformed upward, and a probe tip portion continuing into the tip end side of the deformation portion and extending upward. This is generally shown in Japanese Patent Publication No. 2002-280317, which is incorporated herein by reference in its entirety.
This electrical connecting apparatus includes a guide having an opening opened upward and downward so as to receive a device under test, a sheet-like electrical insulating plate arranged in the opening, an elastic plate made of an electrical insulating material arranged on the electrical insulating plate in the opening, and a sheet-like conductive plate arranged on the elastic plate.
Each contact is supported in the electrical insulating plate and the elastic plate so that its probe rear portion may be located at a slit provided in the electrical insulating plate, and so that its probe tip portion may penetrate the elastic plate to extend upward. The electrical connecting apparatus is incorporated into a wiring board in a state where the deformation portion of each contact is thrust to a conductive portion of the wiring board.
An integrated circuit is inserted in the opening of the guide from the upper side and is received on each contact, and an electrode portion is relatively thrust to the tip end of the probe tip portion of the contact. Accordingly, the contact elastically deforms the elastic plate and is thrust to the conductive portion of the wiring board. As a result, the conductive portion of the wiring board and the electrode portion of the integrated circuit are electrically connected.
At the time of a test, at least one conductive portion and a contact thrust to the conductive portion are used for so-called grounding on the negative side (or the positive side) of the power source, several other conductive portions and contacts thrust to the conductive portions are used for so-called powering on the positive side (or the negative side) of the power source, and the remaining conductive portions and contacts thrust to the conductive portions are used for so-called signaling for supply or taking-out of signals.
In the above state, electrical signals are supplied to the integrated circuit via some contacts for signaling while signals from the integrated circuit are taken out via other contacts for signaling, and thus an electrical test of the integrated circuit is performed.
However, in the conventional electrical connecting apparatuses, since the contact is located in an electrical path between each electrode portion of the integrated circuit and the corresponding conductive portion of the wiring board, the electrical effective length between the electrode portion and the conductive portion is long, and the resistance value between the electrode portion and the conductive portion is large. When the resistance value is large in this manner, a test using high frequency signals cannot be performed accurately.
There is proposed an art in which the apparent resistance value of the contact for grounding or powering is reduced for impedance matching to high frequency signals. This is generally shown in Japanese Patent Publication No. 2007-178165, which is incorporated herein by reference in its entirety.
In Japanese Patent Publication No. 2007-178165, a plurality of through holes and a conductive layer are formed in a plate-like electrical insulating block, contacts of pogo-pin type are arranged in the respective through holes, and at least one contact is made to contact the conductive layer. In this technique, the contact contacting the conductive layer is used for grounding (or powering), and the other contacts are used for powering (or grounding) and signaling.
However, in the above conventional art, since each contact is a pogo-pin type, the structure of the contact itself is complicated. Also, a technique to structure the conductive layer so as to bring the contact into contact therewith is complicated, and it is difficult to bring the contact into contact with the conductive layer reliably.